Recovery nystagmus.

Secondary nystagmus is frequently seen following cessation of prolonged unidirectional vestibular stimulation. It is explained on the basis of an adaptation during the application of the stimulus which leads to an apparent stimulus in the opposite direction when the stimulus is removed. The same phenomenon would be expected with vestibular disease when after a period of adaptation to the vestibular asymmetry, the affected ear recovers some or all of its function. The seondary nystagmus in this instance beats toward the affected ear and has been termed recovery nystagmus because it is generated by recovery of function. Two cases with recovery nystagmus following acute attacks of vertigo are presented.